NO159864B - PROCEDURE FOR DIRECT REDUCTION OF IRON OX SUSTAINABLE MATERIALS FOR FUNGI IRON. - Google Patents

Description

Magnetic data storage element.

The present invention relates to a storage element with several stable states with a closed flux path, which storage element consists of: a thin film of ferromagnetic material which everywhere has the same properties, but which has the four uniaxial anisotropy characteristic properties which produce a magnetically easy axis along which the film's remanent mn~,netization will lie.

: In a three-dimensional element of such a magnetizable material where the thickness is significantly smaller than the length and width, no magnetic domain wall can exist parallel to the large surface of the element.

The advantages of using such a magnetic material as a storage element in electronic data processing systems are well known. However, it is characteristic of such thin films that demagnetization fields arise from the free poles at the edges of the film due to open flux paths. Such demagnetization fields cause the thin films' hysteresis slip characteristics to shift. The effect of demagnetization fields, produced by the. free poles on the edge of the film, consists in causing local magnetization areas (reversed domains) with a magnetization oppositely directed to the main part of the thin film's magnetization. These reversed magnetic fields are separated from the main magnetization of the thin film by either Block or Néelveggér which..have ert. tendency to creep through: the main magnetizing part of the film. when said film is exposed to scattering fields, and thus destroy the information stored in the film. This magnetization creep is the main problem with information storage in thin films. This creeping pattern of reversed magnetization of the small areas with seed poles is. in reality a wall-creep switching phenomenon, which phenomenon is particularly serious because the film 1 can in some cases be demagnetized in a field only one-tenth as strong as required for rotational switching. Such fields can come from the earth's magnetic field, "semiselect!1 or air-coupled random drift fields from the storage system., Por .to achieve therein optimal switching-mode operation. For a thin film, it is fblgly necessary that the reversed";donians on the edge ;i of the film, which domains arise from the free^-polerfp-edges of the film, are eliminated., The problem of dpmane wall creep in. thin films is discussed in an article by Simon Middelhoeckj, Z.'<r> Angew Phys., Vol. I1*, 1962, pages 192-193. (German Journal of .-Applied Physics). <: >Because it is desirable to increase the volumetric performance of the magnetic storage system when using thin films, there has been great interest in finding means by which stbrrelations on the thin films can be reduced. When; the stress on the thin film decreases, the demagnetization field increases, the saturated fields that arise from the free poles on the edge aW eilipø^- The invention relates to the discovery of the fact that if a thin film has a planar circumference which here defined as a "sharp film", the demagnetization fields due to free poles at the edges of the film prevent creep rather than causing it. Such films have much higher creep thresholds than films of conventional types with planar contours. ;According to ...French patent No. 1.307.l<*>+6 it is known to arrange a straight film edge with an angle of ^5° in relation to the easy axis.

The term "sharp film" shall be defined here by a) in the case

a straight-sided film, such as a thin film where the angle between a straight film edge and the field-induced easy axes is everywhere less than ^5°, and b) in the case of a film having a curved contour, such as a thin film where the angle between the tangent at any point on each curved film edge and the field-induced easy axes everywhere is less than . At the edges of such "sharp films" a shaped anisotropy field (i.e., an anisotropy field due to the shape of the thin film element) is provided which is "nearly aligned with the easy axis induced by the film's magnetic field. The resulting anisotropy field 1 such edges is strong and results in a hby opposition to

the formation of reversed domains - which is necessary for creep - e.g. free poles at the edges of the film. The shaped anisotropy induced at such edges in the "sharp film" presupposes the formation of domain walls when such film is affected by weak external fields. Accordingly, a very thin film has been provided which shows a high inherent resistance to the formation of reversed domains at the edges, without being t ■ nbdvéndlg. with elements of hby permeability to end the ' otherwise open flux path, or need for! a complicated cross-sectional contour, for the P.film. • According to the present invention, a : ; Hunting element with several stable states in which for

prevention of magnetization creep the contours of this film are formed so that a) in the case of "straight-sided" film, &r, the angle between a straight film edge and the field-induced easy axis is generally less than ^ 5°, and b) in the case that a film has curved contours, the angle between the tangent to any point on the curved film edge and the field-induced easy axis is everywhere less than 4-5°.

Claims (1)

Storage element with several stable states with an open flux path, which storage element consists of a thin file of ferromagnetic material which everywhere has the same properties, but which has the characteristic properties of uniaxial anisotropy which .produce! a magnetic one axis along which the film's reman^n^© 'magnetization will lie, characterized by ot to prevent magnetization creep in said element, the contours of this film are formed so that a) in the case of the 'straight-sided' filmj is the angle between a straight film edge and the field-in&used '$.ett-e axis everywhere less than 4-5°, and b) in the case that one i" in lm has curved contours, the angle between the tangent to. a hvllScel any point on the curved film edge and the field-induced sixth axis everywhere less than 4-<5>°.